Hermetic compressor

ABSTRACT

A hermetic compressor includes a hermetic container, a motor element, and a compression element. A shaft of the compression element includes a main shaft, a flange projecting from the main shaft, and an eccentric shaft connected to the flange. A main bearing has a thrust surface contacting and sliding on the flange of the shaft. The thrust surface consists of a first portion and a second portion. The first portion is farther from the compression chamber than the center axis is. The second portion is closer to the compression chamber than the center axis is. The area of the first portion is larger than the area of the second portion. This hermetic compressor has a high efficiency and a high reliability.

FIELD OF THE INVENTION

The present invention relates to a hermetic compressor used in a refrigeration cycle of, e.g. a refrigerator.

BACKGROUND OF THE INVENTION

A hermetic compressor includes a hermetic container, a block which is a support frame, a compression element, and a motor element. The compression element is disposed above the block in the hermetic container while the motor element is disposed under the block in the hermetic container.

A shaft having a rotor of the motor element fixed thereto is rotatably supported by a bearing disposed substantially at the center of the block. The shaft rotates to transmit a driving force from the motor element to the compression element.

FIG. 8 is a cross-sectional view of conventional hermetic compressor 500. FIG. 9 is a top view of block 9 of hermetic compressor 500.

Hermetic compressor 500 includes hermetic container 1 and shaft 2. Shaft 2 is press-fitted into rotor 3. Rotor 3 and stator 4 constitute a motor which is a motor element.

One end of connecting rod 5 is connected to crank pin 11 which is an eccentric portion of shaft 2. Piston pin 8 is connected to the other end of connecting rod 5 and is fixed to piston 7. Connection rod 5, piston pin 8, piston 7, and cylinder 6 constitute a compression element. Hermetic container 1 stores refrigerant oil 10 at its bottom.

Crank pin 11 and balance plate 12 are disposed above shaft 2. Crank pin 11 eccentrically rotates to cause piston 7 of the compression element to reciprocate. Thrust surface 14 is provided at the upper end of bearing 15 so as to receive a thrust force. Thrust surface 14 slides directly on a lower surface of balance plate 12. Thrust surface 14 and the lower surface of balance plate 12 constitute a thrust sliding part in hermetic compressor 500.

Conventional hermetic compressor 500 may have its efficiency degrade.

A hermetic compressor similar to hermetic compressor 500 is disclosed in Japanese Patent Laid-Open Publication No. 2000-120540.

SUMMARY OF THE INVENTION

A hermetic compressor includes a hermetic container, a motor element, and a compression element. A shaft of the compression element includes a main shaft, a flange projecting from the main shaft, and an eccentric shaft connected to the flange. A piston reciprocates in a compression chamber in a first direction and a second direction opposite to the first direction. A main bearing has a thrust surface contacting and sliding on the flange of the shaft. The thrust surface consists of a first portion and a second portion. The first portion is farther from the compression chamber than the center axis is in a direction parallel to the first direction. The second portion is closer to the compression chamber than the center axis is in the direction parallel to the first direction. The area of the first portion is larger than the area of the second portion.

This hermetic compressor has a high efficiency and a high reliability.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a cross-sectional view of a hermetic compressor according to Exemplary Embodiment 1 of the present invention.

FIG. 2 is a top view of a cylinder block of the hermetic compressor according to Embodiment 1.

FIG. 3 is a cross-sectional view of an essential part of the hermetic compressor according to Embodiment 1.

FIG. 4 is an enlarged cross-sectional view of an essential part of a motor element of the hermetic compressor according to Embodiment 1.

FIG. 5 shows a change in a repulsive force with a rotation angle of a shaft of the hermetic compressor according to Embodiment 1.

FIG. 6 is a cross-sectional view of a compression element of the hermetic compressor according to Exemplary Embodiment 2 of the invention.

FIG. 7 is an exploded perspective view of a compression element of the hermetic compressor according to Embodiment 2.

FIG. 8 is a cross-sectional view of a conventional hermetic compressor.

FIG. 9 is a top view of a block of the conventional hermetic compressor.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS Exemplary Embodiment 1

FIG. 1 is a cross-sectional view of hermetic compressor 1001 according to Exemplary Embodiment 1 of the present invention. Hermetic compressor 1001 includes hermetic container 101, motor element 105 disposed in hermetic container 101, and compression element 106 disposed in hermetic container 101. Hermetic container 101 is configured to store lubricating oil 102 at a bottom of hermetic container 101. Motor element 105 includes stator 103 and rotor 104. Compression element 106 is disposed above motor element 105 and is driven by motor element 105.

Shaft 110 constituting compression element 106 includes main shaft 111, flange 112, and eccentric shaft 113. Main shaft 111 extends along center axis C111. Flange 112 projects from main shaft 111 away from center axis C111. Eccentric shaft 113 extends in parallel with center axis C111 from upper surface 112A of flange 112. Center axis C111 extends in parallel to direction axis 1001A which is vertical according to Embodiment 1. Main shaft 111 extends from flange 112 in direction 111C extending in parallel to direction axis 1001A. Direction 111C is directed vertically downward according to Embodiment 1. Eccentric shaft 113 is eccentric with respect to main shaft 111. More specifically, eccentric shaft 113 extends from flange 112 along center axis C113 in direction 111D. Center axis C113 is parallel with center axis C111. Direction 111D is opposite to direction 111C, and is directed vertically upward according to Embodiment 1. Rotor 104 is shrink-fitted to main shaft 111. Lubrication mechanism 114 is provided inside shaft 110. Lubrication groove 114A is provided helically in a surface of shaft 110. One end of lubrication groove 114A communicates with lubrication mechanism 114, while the other end extends to lower surface 112B of flange 112.

Cylinder block 115 constituting compression element 106 has substantially cylindrical compression chamber 116 extending in parallel to direction axis 1001B perpendicular to direction axis 1001A. Cylinder block 115 includes main bearing 117 extending in parallel to direction axis 1001A. Main bearing 117 has axial hole 117A for receiving main shaft 111 of shaft 110. Axial hole 117A extends along center axis C117.

Piston 118 is inserted in compression chamber 116 of cylinder block 115 such that piston 118 reciprocates in parallel to direction axis 1001B. Piston 118 includes piston pin 120 extending in parallel to direction axis 1001A. Piston pin 120 and piston 118 are connected to shaft 110 via connection mechanism 119. One end of connection mechanism 119 is rotatably penetrated by piston pin 120, while the other end of connection mechanism 119 is rotatably penetrated by eccentric shaft 113. Compression chamber 116 (piston 118) is positioned from center axis C111 in direction 116A parallel to direction axis 1001B.

Main bearing 117 in cylinder block 115 has flat thrust surface 121 provided on end surface 117C. Thrust surface 121 slides on lower surface 112B of flange 112. When shaft 110 is inserted into axial hole 117A, thrust surface 121 supports a force in the vertical direction generated due to a own weight of rotor 104 and shaft 110, and further supports a force in the vertical direction generated due to the influence of a force generated during the compression of piston 118. Thrust surface 121 and lower surface 112B of flange 112 sliding on each other constitute a thrust sliding part.

FIG. 2 is a top view of thrust surface 121 of cylinder block 115 of hermetic compressor 1001 in view from direction 111C. FIG. 3 is a cross-sectional view of an essential part of hermetic compressor 1001. As shown in FIG. 2, thrust surface 121 entirely surrounds axial hole 117A in a plane flush with thrust surface 121. More specifically, inner periphery 121D of thrust surface 121 entirely surrounds axial hole 117A in the plane flush with thrust surface 121. Thrust surface 121 has outer periphery 121C having a circular shape in view along a direction parallel to direction axis 1001A (FIG. 1). The circular shape has center C121 which is eccentric with respect to center axis C117 of axial hole 117A by predetermined distance L11 in a predetermined direction. More specifically, center C121 of thrust surface 121 is displaced from center axis C117 by predetermined distance L11 in direction 116B opposite to direction 116A directed towards compression chamber 116.

Thrust widths 124 of thrust surface 121 are defined as distances between inner periphery 121D and outer periphery 121C of thrust surface 121 in radial directions with respect to center axis C117. Thrust width 124A which is the smallest width of thrust widths 124 extends in direction 116A from center axis C117 of axial hole 117A, while thrust width 124B which is the largest width of thrust widths 124 extends in direction 116B from center axis C117. Thus, thrust width 124 is largest in direction 116B directed away from compression chamber 116. In other words, the area of thrust surface 121 increases gradually and monotonically in a direction away from compression chamber 116. Thrust surface 121 consists of portions 121A and 121B. Portion 121B positioned in direction 116B is farther from compression chamber 116 than center axis C117 is. Portion 121A positioned in direction 116A is closer to compression chamber 116 than center axis C117 is. The area of portion 121B is larger than that of portion 121A.

Thrust surface 121 has oil groove 127 provided in a portion on thrust surface 121 closest to compression chamber 116. Oil groove 127 extends in parallel to direction axis 1001B which is an axial direction of compression chamber 116. Lubricating oil 102 is pumped by lubrication mechanism 114 from the bottom of hermetic container 101, passes through lubrication groove 114A. Then, lubricating oil 102 passes through oil groove 127 and reaches the thrust sliding part. Lubricating oil 102 mainly lubricates the thrust sliding part constituted by thrust surface 121 and lower surface 112B of flange 112.

Oil groove 127 is located in the position of thrust surface 121 closest to compression chamber 116. This arrangement allows portion 121B farther from compression chamber 116 to have an area large enough to slide on flange 112 of shaft 110.

Thrust surface 121 is processed to have low friction and high hardness by performing a nitriding treatment or a ceramic coating of ceramic, such as CrN, TiN, to thrust surface 121.

FIG. 4 is an enlarged cross-sectional view of an essential part of motor element 105 of hermetic compressor 1001. Stator 103 of motor element 105 includes a core including teeth having windings concentratedly wound around the teeth, thus constituting a concentrated winding structure of motor element 105. Magnetic center 126 of rotor 104 is displaced from magnetic center 125 of stator 103 by predetermined distance L12 in direction 111C. Direction 111C is directed vertically downward according to Embodiment 1.

Motor element 105 can be driven at various rotation speeds by inverter control. According to Embodiment 1, the rotation speed is set to 60 Hz during a normal operation, while the rotation speed is set to 80 Hz as a maximum rotation speed.

Conventional hermetic compressor 500 shown in FIGS. 8 and 9 includes the compression element as the support frame disposed above block 9, and the motor element disposed under block 9. In hermetic compressor 500, a reaction force of the piston load occurs in the compression stroke. The piston load depends on the pressure in cylinder 6 and the bore diameter of cylinder 6. The reaction force acts as a force on a side surface of crank pin 11 of shaft 2.

A clearance ranging from 10 to 30 μm is provided between shaft 2 and bearing 15 of block 9. This clearance causes shaft 2 to incline and contact block 9 in the thrust sliding part or in a journal sliding part. The thrust sliding part is subjected to a force exceeding the own weight of shaft 2 and rotor 3 as a force due to the influence of the piston load.

In compressor 500 including the compression element as the support frame above block 9 and the motor element under block 9, the piston load of piston 7 is added to a thrust force which is the sum of own weights of shaft 2 and rotor 3. The thrust force locally increases a surface pressure of the thrust sliding part, thereby generating a partial contact.

In hermetic compressor 500, the entire thrust sliding part has a large area to prevent the local increase of the surface pressure of the thrust sliding part.

The increase of the sliding area, however, increases the sliding resistance of the thrust sliding part, possibly increasing the sliding loss of the thrust sliding part, accordingly decreasing an efficiency of hermetic compressor 500.

An operation of hermetic compressor 1001 according to Embodiment 1 will be described below. Hermetic compressor 1001 is configured to be connected to a cooling system including refrigerant gas circulating therein.

Upon motor element 105 being energized, rotor 104 rotates shaft 110. This rotation causes eccentric shaft 113 to rotate about center axis C111. The rotation of eccentric shaft 113 transmits to piston 118 via connection mechanism 119, and causes piston 118 to reciprocate in compression chamber 116 in parallel to direction axis 1001B.

The reciprocation of piston 118 causes the refrigerant gas to be sucked into compression chamber 116 from the cooling system, then to be compressed, and to be discharged back to the cooling system.

Piston 118 receives repulsive force F1 applied in direction 116B when compressing the refrigerant gas in compression chamber 116. When shaft 110 rotates, thrust surface 121 provided at upper end surface 117C of cylinder block 115 entirely receives force F3, as shown in FIG. 4. Force F3, is produced due to own weights of rotor 104 and shaft 110, and is directed in direction 111C directed vertically downward along direction axis 1001A. Simultaneously, thrust surface 121 locally receives force F2 which is a component of repulsive force F1 in a direction parallel to direction axis 1001A. Force F2 affects a sliding loss and a surface pressure depending on a contact area between lower surface 112B of flange 112 and thrust surface 121 when lower surface 112B slides on thrust surface 121.

FIG. 5 shows a change of repulsive force F1 with respect to a rotation angle of shaft 110 during a compression stroke of hermetic compressor 1001. In FIG. 5, the horizontal axis represents the magnitude of repulsive force F1, and the vertical axis represents the rotation angle of shaft 110. When the rotation angle is 0 degrees, piston 118 becomes farthest to center axis C111 in direction 116A to compress the refrigerant gas at the highest compression ratio. A sucking stroke in which the refrigerant gas is sucked into compression chamber 116 by piston 118 is executed while the rotation angle of shaft 110 is from 0 degree to 180 degrees. A compression stroke in which the refrigerant gas is compressed is executed while the rotation angle of shaft 110 is from 180 degrees to 360 degrees. Force F2 locally applied in direction 111C parallel to direction axis 1001A to thrust surface 121 due to the influence of repulsive force F1 applied to piston 118 will be described with reference to FIGS. 4 and 5.

Repulsive force F1 applied to piston 118 depends on the pressure in compression chamber 116 and on the inner diameter of compression chamber 116. In the compression stroke, shaft 110 pushes piston 118 in direction 116A. As shown in FIG. 5, repulsive force F1 becomes maximum repulsive force F1max not at 360 degrees, but about 330 degrees in the later stage of the compression stroke, thereby greatly affecting shaft 110 via connection mechanism 119.

In the later stage of the compression stroke during which maximum repulsive force F1max is generated, eccentric shaft 113 is positioned closer in a direction parallel to direction axis 1001B to compression chamber 116 than center axis C117 is. As a result, repulsive force F1 applied to piston 118 is applied to eccentric shaft 113 via connection mechanism 119.

A clearance ranging from 10 to 30 μm is provided between respective diameters of main shaft 111 of shaft 110 and axial hole 117A of main bearing 117. Repulsive force F1 is applied to eccentric shaft 113 in direction 116B. The clearance causes shaft 110 to incline with respect to center axis C117 of axial hole 117A. This inclination causes force F2 which is a component of repulsive force F1 in a direction parallel to direction axis 1001A to be applied to a portion of thrust surface 121 that is opposite to compression chamber 116 with respect to center axis C117.

As a result, force F3 is applied entirely to thrust surface 121 in direction 111C due to the own weights of rotor 104 and shaft 110. Further, force F2 is applied to portion 121B that is on opposite to compression chamber 116 with respect to center axis C111 in direction 111C due to the influence of repulsive force F1.

Center C121 of thrust surface 121 is displaced from center axis C117 of axial hole 117A by predetermined distance L11. This arrangement provides thrust surface 121 with non-constant thrust widths 124 over the entire thrust surface.

More specifically, thrust width 124B of portion 121B of thrust surface 121 which is farther from compression chamber 116 than center axis C117 is has a larger area. Portion 121B exclusively receives force F2 in the vertical direction due to the influence of repulsive force F1 during the compression of piston 118. In contrast, thrust width 124A of portion 121A of thrust surface 121 which is closer to compression chamber 116 than center axis C117 is has a smaller area than thrust width 124B. This structure suppresses an increase of a surface pressure due to force F2 locally applied to thrust surface 121.

This structure provides the thrust sliding part constituted by lower surface 112B of flange 112 and thrust surface 121 with a small sliding loss. The suppression of the increase in the surface pressure of portion 121B receiving force F2 prevents thrust surface 121 from being worn, thereby providing hermetic compressor 1001 with high efficiency and high reliability. This structure allows thrust surface 121 to have a small overall area and further reducing the partial wearing of thrust surface 121, thereby providing hermetic compressor 1001 with high efficiency and high reliability.

Furthermore, this structure allows a large amount of lubricating oil 102 to be supplied to lubricate the sliding part of thrust surface 121 through oil groove 127 of thrust surface 121. Oil groove 127 is formed in small portion 121A of thrust surface 121 having small thrust width 124. This secures the area of the portion of thrust surface 121 that slides on lower surface 112B of flange 112 and that receives a surface pressure, thereby preventing an increase in the surface pressure. As a result, the sliding part of thrust surface 121 is lubricated well, thereby providing hermetic compressor 1001 with high reliability.

Thrust surface 121 is processed to have low friction and high hardness by performing a nitriding treatment or a ceramic coating treatment of ceramic, such as CrN or TiN. These treatments reduce the sliding resistance generated when lower surface 112B of flange 112 contacts and slides on thrust surface 121. As a result, the thrust sliding part has a lower sliding loss, thereby providing hermetic compressor 1001 with high efficiency. Thrust surface 121 having high surface hardness provides the thrust sliding part with high resistant to abrasion.

Thrust surface 121 processed to have low friction and high hardness reduces an area for sliding to the total area of thrust surface 121, thereby reducing friction.

Thrust surface 121 inclines such that portion 121B having force F2 applied thereto in direction 111C is lowered in direction 111C from portion 121A closer to compression chamber 116. That is, thrust surface 121 inclines toward direction 111C along direction 116B. This structure allows lower surface 112B of flange 112 to entirely contact thrust surface 121. This prevents the thrust sliding part from having a partial contact and the local surface pressure, thereby reducing partial wearing.

In motor element 105, magnetic center 126 of rotor 104 is displaced in direction 111C from magnetic center 125 of stator 103, allowing a magnetic attractive force to lift, in direction 111D, shaft 110 fixed to rotor 104. This reduces force F3 applied in vertical direction 111C by the own weights of rotor 104 and shaft 110 while shaft 111 rotates. This reduces the surface pressure of thrust surface 121, and provides hermetic compressor 1001 with high reliability.

As described above, hermetic compressor 1001 includes hermetic container 101, motor element 105, and compression element 106. Motor element 105 is disposed in hermetic container 101 and includes stator 103 and rotor 104. Compression element 106 is disposed in hermetic container 1010 and is driven by motor element 105. Compression element 106 includes shaft 110, cylinder block 115, piston 107, connection mechanism 119, and main bearing 117. Shaft 110 includes main shaft 111 extending along center axis C111, flange 112 projecting from main shaft 111, and eccentric shaft 113 connected to flange 112. Shaft 110 has rotor 104 fixed thereto. Cylinder block 115 has compression chamber 116 located from center axis C111 of main shaft 111 in direction 116A perpendicular to center axis C111. Piston 118 reciprocates in compression chamber 116 in direction 116A and direction 116B opposite to direction 116A. Connection mechanism connects piston 118 and eccentric shaft 113. Main bearing 117 has axial hole 117A supporting main shaft 111 of shaft 110. Main bearing 117 has thrust surface 121 surrounding axial hole 117A. Thrust surface 121 contacts and slides on flange 112 of shaft 110. Thrust surface 121 consists of portions 121A and 121B. Portion 121B is located farther from compression chamber 116 than center axis C111 is in directions 116A and 116B parallel to direction axis 1001A. Portion 121A is located closer to compression chamber 116 than center axis C111 is in directions 116A and 116B parallel to direction axis 1001A. The area of portion 121B is larger than the area of portion 121A.

Thrust surface 121 supports force F3 in vertical direction 111C and force F2 which is a component of repulsive force Fl in vertical direction 111C, Force F3 is generated due to own weights of rotor 104 and shaft 110. Repulsive force F1 is generated due to a compression by piston 118.

Hermetic container 101 is configured to store lubricating oil 102. Thrust surface 121 has oil groove 127 communicating with axial hole 117A. Oil groove 127 allows lubricating oil 102 to pass through oil groove 127. Oil groove 127 is formed in portion 121A of thrust surface 121. Oil groove 127 extends along straight line L101 extending from center axis C111 in direction 116A.

Main shaft 111 of shaft 110 extends from flange 112 in direction 111C perpendicular to direction 116A. Thrust surface 121 inclines in direction 111C along direction 116B.

Rotor 104 of motor element 105 has magnetic center 126 displaced in direction 111C from magnetic center 125 of stator 103. Magnetic center 126 of rotor 104 is positioned under magnetic center 125 of stator 103.

Compression element 106 is disposed above motor element 105 according to Embodiment 1, but may be disposed under motor element 105, providing the same effect.

Exemplary Embodiment 2

FIG. 6 is a cross-sectional view of a compression element of hermetic compressor 1002 according to Exemplary Embodiment 2 of the present invention. FIG. 7 is an exploded perspective view of the compression element of hermetic compressor 1002. In FIGS. 6 and 7, components identical to those of hermetic compressor 1001 according to Embodiment 1 shown in FIGS. 1 to 4 are denoted by the same reference numerals.

Hermetic compressor 1002 according to Embodiment 2 includes annular thrust bearing 210 having thrust surface 121 of hermetic compressor 1001 according to Embodiment 1.

In hermetic compressor 1002, end surface 117C of main bearing 117 of cylinder block 115 has recess 200 therein around axial hole 117A. Thrust bearing 210 is fitted into recess 200. Thrust bearing 210 and radial bearing 117R having axial hole 117A constitute main bearing 117.

Recess 200 has substantially a circular shape. Supporting surface 201 which is a bottom of the recess surrounds axial hole 117A and supports thrust bearing 210. Supporting surface 201 has a width increasing gradually and monotonically from direction 116A approaching compression chamber 116 toward opposite direction 116B. Small recess 202 extending outward is provided in a periphery of recess 200.

Outer periphery 210C of thrust bearing 210 has a circular shape. Thrust bearing 210 has thrust surface 213 which has a shape and function identical to thrust surface 121 according to Embodiment 1. Thrust bearing 210 has a thickness which allows thrust surface 213 to slightly project from recess 200 in direction 111D when thrust bearing 210 is fitted into recess 200. Thrust bearing 210 has through-hole 211 at its center. Through-hole 211 has center C211 which coincides with center axis C117 of axial hole 117A. Thrust bearing 210 has projection 212 on its outer periphery. Projection 212 is engaged with small recess 202 of recess 200.

As described above, main bearing 117 includes thrust bearing 210 and radial bearing 117R having axial hole 117A. Thrust bearing 210 has thrust surface 121, and is a separate component from radial bearing 117R.

Projection 212 is engaged with small recess 202 and prevents thrust bearing 210 from rotating.

At least thrust surface 213 of thrust bearing 210 is processed to have low friction and high hardness by performing a nitriding treatment or a ceramic coating treatment of ceramics, such as CrN or TiN, similarly to the thrust surface according to Embodiment 1.

Thrust surface 213 consists of portions 213A and 213B. Portion 213A is closer to compression chamber 116 than center axis C111 (center C211) is. Portion 213B is farther from compression chamber 116 than center axis C111 (center C211) is. Thrust surface 213 inclines such that portion 213B is lowered in direction 111D from portion 213A by either adjusting the thickness of thrust bearing 210 or processing supporting surface 201 of recess 200.

Thrust bearing 210 has oil groove 214 formed in thrust surface 213 and extending in a radial direction of through-hole 211. Oil groove 214 has a function similar to oil groove 127 according to Embodiment 1. Oil groove 214 is formed at a position of thrust surface 213 that is closest to compression chamber 116 according to Embodiment 2. That is, oil groove 214 extends in direction 116A from center C211.

After being pumped by lubrication mechanism 114 from the bottom of hermetic container 101 and passing through lubrication groove 114A, the lubricating oil passes through oil groove 214 and reaches the thrust sliding part constituted by thrust surface 213 and lower surface 112B of flange 112. The lubricating oil mainly lubricates the thrust sliding part.

An operation of hermetic compressor 1002 according to Embodiment 2 will be described below. Similarly to hermetic compressor 1001 according to Embodiment 1, upon motor element 105 being energized, rotor 104 rotates to cause compression element 106 to operate. As a result, the refrigerant gas is sucked into compression chamber 116 from the cooling system, then compressed there, and discharged back to the cooling system.

In hermetic compressor 1002 according to Embodiment 2, when shaft 110 is rotated, force F3 applied in vertical direction 111C due to the own weights of rotor 104 and shaft 110 shown in FIG. 6 is applied to the entire thrust surface 213 of thrust bearing 210 of main bearing 117. Simultaneously, force F2 which is a component, in vertical direction 111C, of repulsive force F1 during the compression of piston 118 is exclusively applied to portion 213B of thrust surface 213.

Force F2 affects a sliding loss and a surface pressure depending on the contact area between lower surface 112B of flange 112 and thrust surface 213 of thrust bearing 210 when lower surface 112B slides on thrust surface 213. Portion 213B of thrust surface 213 which is farther from compression chamber 116 than center C211 is receives force F2 in directions 116A and 116B parallel to direction axis 1001B. Similar to hermetic compressor 1001 according to Embodiment 1, in hermetic compressor 1002, portion 213B has thrust width 215 which is larger than thrust width 215 of portion 213A that is closer to compression chamber 116 than center C211 is. That is, the area of portion 213B is larger than the area of portion 213A. This structure suppresses an increase of the surface pressure due to force F2 locally applied to thrust surface 213.

This structure also reduces the sliding loss of the thrust sliding part constituted by lower surface 112B of flange 112 and thrust surface 213 of thrust bearing 210 similarly to the compressor according to Embodiment 1. Furthermore, this structure prevents an increase of the surface pressure of portion 213B which exclusively receives force F2 and reduces the partial wear of thrust surface 213, thereby providing hermetic compressor 1002 with high efficiency and high reliability.

Furthermore, a larger amount of lubricating oil 102 is supplied to lubricate the sliding part of thrust surface 213 through oil groove 214 formed in thrust surface 213 of thrust bearing 210. Thrust surface 213 includes portion 213A having a smaller width than thrust width 215. This structure secures a large sliding area of portion 213B that is subjected to the surface pressure, thereby preventing an increase in the surface pressure. As a result, the sliding part of thrust surface 213 of thrust bearing 210 is lubricated well, thereby providing hermetic compressor 1002 with high reliability.

Thrust surface 213 is processed to have low friction and high hardness by performing a nitriding treatment or a ceramic coating treatment of ceramics, such as CrN or TiN. This treatment reduces the sliding resistance generated when lower surface 112B of flange 112 slides on thrust surface 213. As a result, the thrust sliding part constituted by lower surface 112B of flange 112 and thrust surface 213 has a lower sliding loss, thereby providing hermetic compressor 1002 with high efficiency. Thrust surface 213 having high surface hardness makes the thrust sliding part more abrasion resistant.

Thrust surface 213 processed to have low friction and high hardness reduces an overall area of thrust surface 213 of thrust bearing 210, thereby reducing friction.

Thrust bearing 210 is a separate component from main bearing 117 (radial bearing 117R), and is processed separately from main bearing 117. This arrangement allows thrust surface 213 to be subjected to the nitriding treatment or the ceramic coating treatment, or to incline in direction 111C along direction 116B.

As a result, the degree of the ceramic coating can be adjusted and set easily and inexpensively, thereby easily processing the inclination of thrust surface 213. Thrust bearing 210 can be applied to various compressors having different capacities.

According to Embodiment 2, thrust surface 213 can be applied to a hermetic compressor in which compression element 106 is disposed under motor element 105, providing the same effects.

Hermetic compressors 1001 and 1002 according to Embodiments 1 and 2 which have high reliability due to the low sliding loss of the thrust sliding part are applicable to air conditioners, fridge-freezers, and other types of freezers.

The present invention is not limited to Embodiment 1 or 2. 

1. A hermetic compressor comprising: a hermetic container; a motor element disposed in the hermetic container, the motor element including a stator and a rotor; and a compression element disposed in the hermetic container, the compression element being driven by the motor element, wherein the compression element includes: a shaft including a main shaft extending along a center axis, a flange projecting from the main shaft, and an eccentric shaft connected to the flange, wherein the shaft has the rotor fixed thereto, a cylinder block having a compression chamber located from the center axis of the main shaft in a first direction perpendicular to the center axis; a piston reciprocating in the compression chamber in the first direction and a second direction opposite to the first direction; a connection mechanism connecting the piston and the eccentric shaft; and a main bearing having an axial hole supporting the main shaft of the shaft, the main bearing having a thrust surface surrounding the axial hole, the thrust surface contacting and sliding on the flange of the shaft, wherein the thrust surface consists of a first portion and a second portion, the first portion being farther from the compression chamber than the center axis is in a direction parallel to the first direction, the second portion being closer to the compression chamber than the center axis is in the direction parallel to the first direction, and wherein an area of the first portion is larger than an area of the second portion.
 2. The hermetic compressor of claim 1, wherein the thrust surface supports a force in a vertical direction and a component of a repulsive force in the vertical direction, the force in the vertical direction being generated due to own weights of the rotor and the shaft, the repulsive force being generated due to a compression by the piston.
 3. The hermetic compressor of claim 1, wherein the hermetic container is configured to store lubricating oil; and wherein the thrust surface has an oil groove communicating with the axial hole, the oil groove allowing the lubricating oil to pass through the oil groove.
 4. The hermetic compressor of claim 3, wherein the oil groove is formed in the second portion of the thrust surface.
 5. The hermetic compressor of claim 4, wherein the oil groove extends along a straight line extending from the center axis in the first direction.
 6. The hermetic compressor of claim 1, wherein the main shaft of the shaft extends from the flange in a third direction perpendicular to the first direction; and wherein the thrust surface inclines in the third direction along the second direction.
 7. The hermetic compressor of claim 1, wherein the thrust surface has a nitriding treatment and a ceramic coating treatment performed thereto.
 8. The hermetic compressor of claim 1, wherein the main bearing includes: a radial bearing having the axial hole; and a thrust bearing having the thrust surface, the thrust bearing being a separate component from the radial bearing.
 9. The hermetic compressor of claim 1, wherein the main shaft of the shaft extends from the flange to a third direction perpendicular to the first direction; and wherein the rotor of the motor element has a magnetic center displaced in the third direction from a magnetic center of the stator.
 10. The hermetic compressor of claim 9, wherein the magnetic center of the rotor is positioned under the magnetic center of the stator. 